EP3499869B1

EP3499869B1 - Pixel sensing module and image capturing device

Info

Publication number: EP3499869B1
Application number: EP17902588.7A
Authority: EP
Inventors: Wei-Min Chao; Chien-Jian Tseng
Original assignee: Shenzhen Goodix Technology Co Ltd
Current assignee: Shenzhen Goodix Technology Co Ltd
Priority date: 2017-10-20
Filing date: 2017-10-20
Publication date: 2022-05-04
Anticipated expiration: 2037-10-20
Also published as: US20190123076A1; US10644045B2; WO2019075750A1; EP3499869A4; CN107980219A; EP3499869A1; CN107980219B

Description

Field of the Invention

The present application relates to a pixel sensing module and an image capturing device, and more particularly, to a pixel sensing module and an image capturing device capable of enhancing light sensitivity.

Background

CMOS image sensor (CIS) has been widely applied in electronic devices with image capturing function and digital camera. In general, the image sensor comprises a pixel sensing array, and the pixel sensing array comprises a plurality of pixel sensing unit arranged in an array. The pixel sensing unit comprises a light-sensing component, such as a photo diode or a photo transistor, and a converting circuit. The sensitivity of the pixel sensing unit is related/proportional to a light-sensing area of the light-sensing component. Take the pixel sensing unit comprising the photo diode as an example, the photo diode stores the electronic charges caused by the light in the potential well of the photo diode, and the electronic charges is converted by the converting circuit comprising transistors into voltage signal, where the voltage signal is the pixel value corresponding to the pixel sensing unit. Light sensitivity of the pixel sensing unit is related to an area of the photo diode in the circuit layout.
To achieve a specific light sensing capability for the image sensor, the pixel sensing unit is required to have a certain light sensing area. In the prior art, each pixel sensing unit only comprises a light sensing component. In other words, the only light sensing component of the pixel sensing unit has to have the required light sensing area of the pixel sensing unit. However, for the light sensing component with large light sensing area, the electronic charges within the potential well is not easy to be completely drained out by the converting circuit, such that the light-sensing component may have residual electronic charges, which may cause unnecessary image sticking effect on the digital camera. In addition, the image sensor comprises a collimator in general. For example, the image sensors in US 2010/238330 A1 , US 2011/261239 A1 , US 2006/011852 A1 and EP 2 833 623 A1 ) comprise collimators. The collimator is configured to project the light onto the pixel sensing unit. However, the pixel sensing unit and the collimator are not perfectly aligned, such that crosstalk exists between light paths.
Therefore, it is necessary to improve the prior art.

Summary

It is therefore an objective of embodiments of the present application to provide a pixel sensing unit and an image capturing device, to improve over disadvantages of the prior art.
To solve the problem stated in the above, an embodiment of the present application is disclosed in claim 1.
For example, a first opening among the plurality of openings faces at least a sub-pixel light-sensing component among the plurality of sub-pixel light-sensing components.
For example, the plurality of sub-pixel light-sensing components comprises photo diodes.
For example, the integrating unit performs an average operation on the plurality of sub-pixel values, to output the pixel value as an average of the plurality of sub-pixel values.
For example, the integrating unit performs a summation operation on the plurality of sub-pixel values, to output the pixel value as a summation of the plurality of sub-pixel values.
For example, the integrating unit outputs the pixel value as a sub-pixel value among the plurality of sub-pixel values.
For example, the plurality of sub-pixel light-sensing components of the pixel light-sensing unit arranged in a sub-array, each of the openings of the collimating unit faces a plurality of sub-pixel light-sensing components in the sub-array, and the projections of the plurality of openings onto the light receiving side are not overlapped with each other.
For example, the pixel light-sensing unit comprises N*N sub-pixel light-sensing components, the N*N sub-pixel light-sensing components are formed as multiple sub-pixel groups, each of the sub-pixel groups comprises M*M sub-pixel light-sensing components; each of the openings of the collimating unit faces a sub-pixel group; wherein N, M are both integer greater than one, M<N, and N is a multiple of M_∘
For example, the pixel light-sensing unit comprises 16 sub-pixel light-sensing components, and N=4, M=2.
For example, the light-sensing area and the non-light-sensing area of each of the sub-pixel light-sensing components are located at a corner region of the sub-pixel light-sensing components.
For example, the collimating unit further comprises a plurality of lenses, and each of the lenses is arranged at a respective opening of the collimating unit.
An embodiment of the present application provides an image capturing device according to claim 12.
The present application utilizes the collimating unit having a plurality of openings aligned with the zone of the pixel light-sensing unit at the light receiving side so as to avoid crosstalk between the light paths and achieve the maximum light amount; and utilizes the plurality of sub-pixel light-sensing components of the pixel light-sensing unit to enhance the draining-out capability. Furthermore, the present application arranges the sub-pixel light-sensing components appropriately, such that the projections of the openings at the light receiving side (i.e., the light transmission zone) only overlap with the light-sensing areas of the sub-pixel light-sensing components and do not overlap with the non-light-sensing area of the plurality of sub-pixel light-sensing components, to achieve better light sensitivity.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

Brief Description of the Drawings

FIG. 1 is a schematic diagram of an image capturing device according to an embodiment of the present application;
FIG. 2 is a side view of a pixel sensing module according to an embodiment of the present application;
FIG. 3 is a top view of a pixel light-sensing unit according to an embodiment of the present application;
FIG. 4 is a top view of a sub-pixel light-sensing component according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application become more apparent, the following relies on the accompanying drawings and embodiments to describe the present application in further detail. It should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the present application.
Please refer to FIG. 1 to FIG. 3. FIG. 1 is a schematic diagram of an image capturing device 10 according to an embodiment of the present application. FIG. 2 is a schematic diagram of a pixel sensing module PXM according to an embodiment of the present application. FIG. 3 is a top view of a pixel light-sensing unit PX according to an embodiment of the present application. The image capturing device 10 may be CMOS image sensor (CIS), which may be applied to a device which needs to capture images such as an optical fingerprint identification or a camera. As shown in FIG. 1, the image capturing device 10 comprises a plurality of pixel sensing modules PXM. The plurality of pixel sensing modules PXM is arranged as an array. The plurality of pixel sensing modules PXM outputs a plurality of pixel values VP corresponding to an image for the backend circuit or the device to perform an image processing or operation(s) .
As shown in FIG. 2 and FIG. 3, the pixel sensing module PXM comprises the pixel light-sensing unit PX and a collimating unit CM. Each pixel light-sensing unit PX receives light at a light receiving side PI, drains out the photo electronic charges generated by the light, and outputs the pixel value VP corresponding to the pixel light-sensing unit PX. However, for the pixel light-sensing component with large light-sensing area, the photo electronic charges stored in the pixel light-sensing component are not easily drained out, such that residual electronic charges are left in the light-sensing components, and cause unnecessary image sticking effect on the image capturing device. To solve the problem of the residual photo electronic charges, the pixel light-sensing component with large light-sensing area may be partitioned into sub-pixel light-sensing components with small light-sensing area, such that the photo electronic charges are easily drained out.
In detail, the pixel light-sensing unit PX comprises a plurality of sub-pixel light-sensing components SPX and an integrating unit 20. Moreover, if the pixel light-sensing unit PX needs to have a light-sensing area to achieve a certain light sensitivity, a summation of a plurality of sub-light-sensing areas corresponding to the plurality of sub-pixel light-sensing components SPX is substantially the light-sensing area. The sub-pixel light-sensing component SPX may comprise a photo diode, which may output a corresponding sub-pixel value SVP. The integrating unit 20 is coupled to the plurality of sub-pixel light-sensing components SPX, to receive a plurality of sub-pixel values SVP corresponding to the plurality of sub-pixel light-sensing components SPX. The integrating unit 20 is configured to integrate the plurality of sub-pixel values SVP as the pixel value VP. In other words, the integrating unit 20 may output one single pixel value VP according to the plurality of sub-pixel values SVP corresponding to the plurality of sub-pixel light-sensing components SPX.
Take the pixel light-sensing unit PX illustrated in FIG. 3 as an example, the pixel light-sensing unit PX comprises 16 sub-pixel light-sensing components SPX. The 16 sub-pixel light-sensing components SPX are all located within a zone ZN at the light receiving side P1 and arranged as a 4×4 array. The 16 sub-pixel light-sensing components SPX output 16 sub-pixel values SVP to the integrating unit 20. The integrating unit 20 outputs the single pixel value VP according to the 16 sub-pixel values SVP.
In another perspective, the collimating unit CM may comprise a plurality of lenses LN and a plurality of openings H. The opening H is located at a light transmission portion at a bottom of the collimating unit CM. Through the lenses LN and the openings H, light outside the image capturing device 10 may be transmitted through the collimating unit CM and irradiated onto the pixel light-sensing unit PX. In other words, the plurality of openings H of the collimating unit CM is aligned with the pixel light-sensing unit PX, i.e., projections of the plurality of openings H of the collimating unit CM onto the plane at which the pixel light-sensing unit PX is located (the light receiving side of the pixel light-sensing unit PX) are completely located within the zone ZN of the single pixel light-sensing unit PX at the light receiving side P1. In other words, the light transmitted through the collimating unit CM would be irradiated onto the pixel light-sensing unit PX, and would not be irradiated on adjacent pixel light-sensing units. The crosstalk between the light paths is avoided, and a maximum light amount is achieved. A projection of the openings H onto the light receiving side P1 is called as a light transmission zone HP. For example, in FIG. 3, 4 light transmission zones HP are illustrated on the 16 sub-pixel light-sensing components SPX. That is, in the current embodiment, the collimating unit CM comprises 4 openings H. Each openings H are aligned to 4 sub-pixel light-sensing components SPX. The projection of the each openings H onto the light receiving side P1 (i.e., the light transmission zone HP) is located within the zone ZN of the pixel light-sensing unit PX. In addition, even though the light transmitted through the collimating unit CM would be irradiated onto the plurality of sub-pixel light-sensing components SPX of the pixel light-sensing unit PX, the plurality of sub-pixel values SVP outputted by the plurality of sub-pixel light-sensing components SPX is corresponding to the single pixel value VP corresponding to the pixel light-sensing unit PX, which means that the light transmitted through the collimating unit CM would not cause crosstalk to the neighboring pixel light-sensing unit, such that the crosstalk between the light paths is avoided.
Furthermore, please refer to FIG. 4. FIG. 4 is a layout schematic diagram (top view) of a sub-pixel light-sensing component SPX according to an embodiment of the present application. The sub-pixel light-sensing component SPX may comprise a light-sensing area LSA, a transmission gate TX and a floating node FD. The light-sensing area LSA receives light and produces photo electronic charges. The transmission gate TX is configured to apply a signal S_TX to drain out the photo electronic charges stored in the light-sensing area LSA to the floating node FD, and the sub-pixel value SVP is related to an amount of the photo electronic charges in the floating node FD of the sub-pixel light-sensing component SPX.
Since the light-sensing area LSA receives light and a location of which is related to the light sensitivity of the sub-pixel light-sensing component SPX. The transmission gate TX and the floating node FD do not receive light and a location of which is irrelevant to the light sensitivity of the sub-pixel light-sensing component SPX. Hence, the location of the transmission gate TX and the floating node FD at the light receiving side P1 may be regarded as the non-light-sensing area of the sub-pixel light-sensing component SPX. In this case, to enhance the light sensitivity of the pixel light-sensing unit PX, an arrangement of the plurality of sub-pixel light-sensing components SPX of the pixel light-sensing unit PX may be adjusted, such that the light transmission zone HP, the projection of the openings H onto the light receiving side P1 of the pixel light-sensing unit PX, only overlaps with the light-sensing areas LSA of the plurality of sub-pixel light-sensing components SPX, and the light transmission zone HP does not overlap with the non-light-sensing areas of the plurality of sub-pixel light-sensing components SPX. Therefore, the pixel light-sensing unit PX would have better light sensitivity.
In addition, the method of the integrating unit 20 integrating the plurality of sub-pixel values SVP as the pixel value VP is not limited. In an embodiment, the integrating unit 20 may perform an average operation on the plurality of sub-pixel values SVP, to output the pixel value VP as an average of the plurality of sub-pixel values SVP. In an embodiment, the integrating unit 20 may perform a summation operation on the plurality of sub-pixel values SVP, to output the pixel value VP as a summation of the plurality of sub-pixel values SVP. In an embodiment, the integrating unit 20 may choose one sub-pixel value SVP among the plurality of sub-pixel values SVP to be the pixel value VP, and output the pixel value VP as the chosen sub-pixel value SVP.
Notably, the embodiments stated in the above are utilized for illustrating the concept of the present application. Those skilled in the art may make modifications and alterations accordingly, and not limited herein. For example, in the present application, the sub-pixel light-sensing components of the pixel light-sensing unit are not limited to be arranged as the 4×4 array. The pixel light-sensing unit is not limited to including 16 sub-pixel light-sensing components. The sub-pixel light-sensing components within the pixel light-sensing unit may be arranged in different ways, depending on the practical situation, and not limited thereto.
In summary, the present application utilizes the collimating unit having a plurality of openings aligned with the zone of each pixel light-sensing unit at the light receiving side so as to avoid crosstalk between the light paths and achieve the maximum light amount; and utilizes the plurality of sub-pixel light-sensing components of the pixel light-sensing unit to enhance the draining-out capability. Furthermore, the present application arranges the sub-pixel light-sensing components appropriately, such that the projections of the openings at the light receiving side (i.e., the light transmission zone) only overlap with the light-sensing areas of the sub-pixel light-sensing components and do not overlap with the non-light-sensing area of the plurality of sub-pixel light-sensing components, to achieve better light sensitivity.
The above disclosure should be construed as limited by the subject-matter of the appended claims.

Claims

A pixel sensing module (PXM), comprising:
a pixel light-sensing unit (PX), for receiving light at a light receiving side (P1) and outputting a pixel value, the pixel light-sensing unit (PXM) comprising:
a plurality of sub-pixel light-sensing components (SPX), configured to output a plurality of sub-pixel values, wherein each sub-pixel light-sensing component comprises a light-sensing area (LSA), a transmission gate (TX) and a floating node (FD), and the transmission gate and the floating node are arranged in a non-light-sensing area, and the transmission gate is arranged between the light-sensing area and the floating node, wherein the light-sensing area is configured to receive light and produces photo electronic charges, the transmission gate is configured to apply a signal to drain out the photo electronic charges stored in the light-sensing area to the floating node, wherein the respective subpixel value is related to the photo electronic charges in the floating diffusion node; and

an integrating unit (20), coupled to the pixel light-sensing unit, configured to output the pixel value according to the plurality of sub-pixel values; and

a collimating unit (CM), having a plurality of openings (H), wherein the plurality of openings (H) are aligned with an area of the pixel light-sensing unit, and projections (HP) of the plurality of openings onto the light receiving side (P1) lie within the area of the pixel light-sensing unit at the light receiving side (PI);

characterized in that

the projections (HP) of the plurality of openings (H) only overlap with the light-sensing areas of the plurality of sub-pixel light-sensing components (SPX), and the projections (HP) do not overlap with the non-light-sensing areas of the plurality of sub-pixel light-sensing components (SPX).
The pixel sensing module of claim 1, characterized in that, a first opening among the plurality of openings faces at least a sub-pixel light-sensing component (SPX) among the plurality of sub-pixel light-sensing components (SPX) at the light receiving side.
The pixel sensing module of claim 1, characterized in that, the plurality of sub-pixel light-sensing components (SPX) comprises photo diodes.
The pixel sensing module of claim 1, characterized in that, the integrating unit is configured to perform an average operation on the plurality of sub-pixel values, to output the pixel value as an average of the plurality of sub-pixel values.
The pixel sensing module of claim 1, characterized in that, the integrating unit is configured to perform a summation operation on the plurality of sub-pixel values, to output the pixel value as a summation of the plurality of sub-pixel values.
The pixel sensing module of claim 1, characterized in that, the integrating unit is configured to output the pixel value as a sub-pixel value among the plurality of sub-pixel values.
The pixel sensing module of claim 1, characterized in that, the plurality of sub-pixel light-sensing components (SPX) of the pixel light-sensing unit are arranged in sub-arrays, each of the openings of the collimating unit faces a plurality of sub-pixel light-sensing components (SPX) in a respective sub-array, and the projections of the plurality of openings onto the light receiving side (P1) are not overlapped with each other.
The pixel sensing module of claim 7, characterized in that, each sub-array N*N sub-pixel light-sensing components (SPX), the N*N sub-pixel light-sensing components (SPX) are formed as multiple sub-pixel groups, each of the sub-pixel groups comprises M*M sub-pixel light-sensing components (SPX) ; each of the openings of the collimating unit faces a sub-pixel group; wherein N, M are both integer greater than one, M<N, and N is a multiple of M_∘
The pixel sensing module of claim 8, characterized in that, the pixel light-sensing unit comprises 16 sub-pixel light-sensing components, and N=4, M=2.
The pixel sensing module of claim 1, characterized in that, the light-sensing area and the non-light-sensing area of each of the sub-pixel light-sensing components are located at a corner region of the sub-pixel light-sensing components.
The pixel sensing module of claim 1, characterized in that, the collimating unit further comprises a plurality of lenses, and each of the lenses is arranged at a respective opening of the collimating unit.
An image capturing device, characterized by, comprising:
a plurality of pixel sensing modules, arranged as an array, wherein each pixel sensing module is a pixel sensing module of any one of claims 1-11.